Cobalt-site cerium doped SmxSr1−xCoO3−δ oxides as potential cathode materials for solid-oxide fuel cells

A series of new oxides with the nominal composition of SmxSr1−xCo1−yCeyO3−δ (x = 0.1, 0.3, 0.5; y = 0.05, 0.1) were synthesized. Their crystal structure, morphology, thermal expansion and electrochemical properties were systematically investigated. A phase-pure perovskite-type Sm0.3Sr0.7Co0.95Ce0.05O3−δ oxide is obtained, while the other samples are actually composed of B-site cation deficient SmxSr1−xCo1−yCey−zO3−δ (0 < z < y) and CeO2 mixed phases. These two-phase samples exhibit larger oxygen nonstoichiometry (δ) and higher average thermal expansion coefficients (TEC), while the single-phase Sm0.3Sr0.7Co0.95Ce0.05O3−δ oxide shows a smaller δ and a lower TEC as compared to Sm0.3Sr0.7CoO3−δ. The introduction of cerium also effectively suppresses the chemical expansion and the growth of grain particles. The smaller grain size is beneficial in improving the electrode surface area. In addition, the electrical conductivities of Ce-doped SmxSr1−xCoO3−δ are all higher than 200 S cm−1. EIS tests demonstrate that partially substituting Co with Ce and the B-site deficiency improve the cathode performance. Sm0.3Sr0.7Co0.95Ce0.05O3−δ shows the lowest area specific resistance (ASR) among the others. Through proper cobalt-site cerium doping, the SmxSr1−xCoO3−δ related oxides could be developed into promising cathode materials for SOFC.